The present invention relates to a servo information writing method and a storage device for recording servo information including phase servo patterns discretely in a track direction of respective data surfaces of plural media and reproducing the servo information by means of heads provided with write heads and read heads integrally, and particularly relates to a servo information writing method and a storage device which do not require correction of position signals at the time of switching the heads even if read heads displace physically.
Conventionally, in a magnetic disk apparatus manufacturing process, at the stage that a disk enclosure is assembled and manufactured, servo patterns are written onto data surfaces of media by a servo track writer (STW), namely, servo patterns are servo-written. In the servo write using the servo track writer, heads are moved and located in objective cylinder positions successively by a laser locating apparatus or the like from an outer side towards an inner side. Write heads of the respective heads provided correspondingly to the data surfaces in the cylinder positions are switched successively so that the servo patterns are written onto the same cylinder positions of the respective data surfaces. For this reason, the positions of the servo patterns written onto the respective data surfaces are determined by positions of the write heads of the respective heads.
In order to cope with recent large capacity and high recording density, as a recording/reproduction head to be used in a magnetic disk apparatus, a combined head, in which a write head using an inductive head and a read head using, for example, an MR head are integrated, is used. Since the write head and the read head are different from each other physically, their relative positions disperse.
FIG. 1A shows an arrangement of a write head and a read head in a downward No. 1 head 200 which is arranged on a front data surface of a medium. FIG. 1B shows an arrangement of a write head and a read head in an upward No.2 head 202 which is arranged on a rear surface of the same medium. In the No. 1 head 200, a track center 216 of the read head 208 displaces from a track center 212 of the write head 204 towards an inner side by +D1. On the contrary, in the No. 2 head 202, a track center 218 of the read head 210 displaces from a track center 214 of the write head 206 towards an outer side by xe2x88x92D2. Since the No. 1 head 200 faces downward and the No. 2 head 202 face upward, their displacement directions are opposite to each other.
FIGS. 2A and 2B show displacement of the track centers in the case where servo patterns are recorded onto the same cylinder and read therefrom by the heads 200 and 202 shown in FIGS. 1A and 1B. At first, in the No. 1 head 200 in FIG. 2A, a phase is displaced to both sides of the track center 212 by the write head 204 and servo patterns A and 2B of a write track width are recorded alternatively. Similarly, in the No. 2 head 202 in FIG. 2B, a phase is displaced to both sides of the track center 214 by the write head 206 and servo patterns A and B of a write track width are recorded alternatively. The servo patterns A and B are read by the read heads 208 and 210 having amounts xe2x88x92D1 and +D2 of displacement from the track centers 212 and 214, and track centers which satisfy the following relationship:
(pattern A read signal)=(pattern B read signal)
are obtained. In this case, the write head 204 has a track center 220 and the write head 206 has a track center 222, and the track centers of the respective write heads are different from each other due to the respective read heads.
Further, such heads are mounted to rotary actuators, and an offset amount is different in respective cylinder positions. FIG. 3 shows an example of the No. 1 head 200. In the case where the head 200 is located on a medium surface 228 by a rotary actuator 226 having a rotational center 224, an offset is zero in a center position where a yaw angle xcex8 is zero, but the offset is large according to yaw angles xcex81 and xcex82 on innermost and outermost positions. The directions of the offset are opposite to each other in the outer and inner sides. For this reason, in the case where the heads are located in positions where read signals of the servo patterns A and B are equal to each other by the read heads 208 and 210 at the time of data writing as shown in FIGS. 2A and 2B, a condition that the read signals of the servo patterns A and B are equal to each other fails every time when the head is switched in the same cylinder position. As a result, the head should be relocated at every time of switching.
In one method to eliminate the relocating due to switching of the heads, a displacement amount of the write head and the read head in each head is previously measured, displaced position signals are offset so as to be correct position signals. For example since an offset of the No. 1 head is D1, the offset D1 is added to the position signal of the track center 220 where the read signals of the servo patterns A and B are equal to each other so that the correct position signal of the track center 212 can be obtained.
Due to such offset correction of the position signal, although a value of the position signals on the track center changes every time when the heads are switched, the heads do not move physically. However, in this case, displacement amounts of the write heads and the read heads in each head and each cylinder position are stored in a memory of the magnetic disk apparatus, and the displacement amounts should be read out from the memory in each head and each cylinder and the position signals should be corrected. For this reason, in the case, for example, where a number of heads is four and each data surface has 2000 cylinders, it is necessary to store 8000 displacement amounts onto the memory, and a memory capacity of the apparatus becomes larger.
In addition, in another solving method, the servo patterns A and B are displaced to the center position of the read heads so as to be written at the time of servo write using the servo track writer (STW), and the track centers read by the read head coincide with each other in each head. For example, in the No. 1 head 200 shown in FIG. 2A, the write head 204 is offset to the inner side by the shift amount D1 of the read head 208, and the servo patterns A and B are written. Moreover, in the No. 2 head 202 shown in FIG. 2B, the write head 206 is offset to the outer side by the shift amount D2 of the read head 210, and the servo patterns A and B are written. However, in this method, the offset operation of the head is required every time when the servo patterns of each head are written, thereby requiring long time for the servo writing operation. As a result, there arises a problem that the producing efficiency is deteriorated.
The present invention provides a servo information writing method and a storage device which uses phase servo patterns as position information of servo information, and does not require an offset operation at the time of writing corrected servo patterns of position signals at the time of switching heads even if physical displacement occurs on respective read heads.
The present invention provides a servo information writing method of writing servo information including phase servo patterns discretely in a track direction onto data surfaces of plural media in a magnetic disk apparatus in which heads integrally having write heads and read heads are arranged correspondingly to the data surfaces of the plural media.
(Phase Servo Writing which Eliminates Displacement of Read Head)
A servo information writing method is characterized by including:
the measuring step of measuring displacement amounts D of the read heads with respect to the write heads in each head and each cylinder position on the media surfaces; and
the position information writing step of adjusting phases of the phase servo patterns based on the measured displacement amounts D so that relative displacement amounts between the read heads are eliminated in each head and each cylinder position of the media surfaces so as to write the phase servo patterns. According to the phase servo patterns recorded by such a servo information writing method, even if relative displacement exist between the read heads, a chanqe in the head position signals detected from the phase servo patterns due to the head switching is enough small to be ignored. For this reason, time for locating at the time of head switching is shortened, and access stopping time for this time can be shortened so that the performance of the apparatus can be improved. Moreover, since it is not necessary to store displacement amounts to be used for correcting the position signals, a memory capacity of the apparatus is reduced. Further, offset seek of the write heads at the time of servo write is not required, and thus operating efficiency of the servo write can be improved.
Here, the position information writing step adjusts the phases of the phase servo patterns so that a relative displacement amount a of another read head, for example a No. 2 head, with respect to a specified read head (No. 1 head) is eliminated and writes the phase servo patterns. More concretely, the relative displacement amount a (=D1+D2) of another read head with respect to a specified read head is calculated from the measured displacement amounts D1 and D2 of the read heads with respect to the write heads in each cylinder position of each head, and the relative displacement amount a is converted into a phase angle xcfx86 of the phase servo patterns. The phase servo patterns are written onto the media surfaces of the specified head in each cylinder position in a state that the phase angle xcfx86 is zero, and finally the phase servo patterns are displaced by the phase angle xcfx86 so as to be written onto the media surfaces of the read heads other than the specified head.
Further, in another form, the position information writing step adjusts the phases of the phase servo patterns so that relative displacement amounts of the read heads with respect to the write heads, namely, the measured displacement amounts D are eliminated so as to write the phase servo patterns. More concretely, the measured values of the displacement amounts D of the read heads with respect to the write heads are converted into phase angles xcfx86 of the phase servo patterns in each cylinder position of each head, and the phase servo patterns are displaced by the phase angle xcfx86 in each cylinder position of each head so as to be written. Here, in the case where the phase servo patterns are recorded in a state that N cylinders form 1 unit, the position information writing step calculates the phase angle xcfx86 from the phase displacement amount (xcex1 or D) according to the following equation:
xcfx86=(360xc2x0/N)xc2x7(displacement amount)
In the case, for example, where the phase servo patterns are recorded for each four cylinders, the phase angle xcfx86 is calculated from the displacement amount (xcex1, D) according to the following equation:
xcfx86=90xc2x0xc2x7(displacement amount).
The position information writing step converts the phase angle xcfx86 into delay time xcfx84d so as to set it to a programmable delay line, and changes the phases of writing reference clocks read from the media surfaces so as to adjust the writing phases of the phase servo patterns.
The measuring step measures the displacement amounts D of the read heads with respect to the write heads by means of measuring cylinders in a plurality of positions from the outer to inner sides of the respective media surfaces. Moreover, the position information writing step obtains displacement mounts of non-measuring cylinders from the displacement amounts of the measuring cylinder by means of interpolation, and adjusts the phases of the phase servo patterns so that the relative displacement amounts between the read heads based on the measured displacement amounts and the interpolated displacement amounts, and writes the phase servo patterns. Further, the measuring step writes a pair of burst patterns onto both sides of the track center alternatively by means of the write heads in each measuring cylinder with the phases being displaced, and measures the displacement amounts D of the read heads with the write heads based on head moving amounts to a position where read signals the paired burst patterns by means of the read heads are equal to each other.
Meanwhile, since the present invention does not require an offset operation of the write heads, at the time of switching the heads, when the displacement amount of the read heads is increased, the reads heads exceed a boundary of the tracks so as to be overlapped on the cylinder information using the burst patterns included in the servo information in the adjacent cylinder. As a result, misreading of the cylinder information possibly occurs. Therefore, the servo information writing method of the present invention further includes the cylinder information writing step of offsetting cylinder information to be written with the phase servo patterns according to the displacement amounts of the read heads with respect to the write heads in each head and each cylinder position so as to write the cylinder information. The cylinder information writing step, in the case where the phase servo patterns are displaced by (1/n) track pitch unit for 1 cylinder in a state that N cylinders form 1 unit so as to be recorded, converts the displacement amounts of the read track center into head feeding amounts for (1/n) track pitch unit so as to offset-seek the phase servo patterns. As a result, the cylinder information can be offset-written by directly using the feeding pitch at the time of writing the phase servo patterns. In the cylinder information writing step, in the case where the cylinder information which is not subject to offset seek is adjacent to the cylinder information which is subject to be offset seek and written, one of the information is narrower than 1 track width, and the other is wider than 1 track width.
In addition, the present invention provides a storage device which does not require correction of position signals at the time of switching the heads even if physical displacement occurs in each read head. The storage device is constituted so that a plurality of heads integrally having write heads and read heads corresponding to data surfaces of plural media are located in arbitrary cylinder positions so as to perform recording/reproduction, and servo information including phase servo patterns is discretely recorded onto the data surfaces of the plural media in a track direction. The storage device of the present invention is characterized in that the phase servo patterns in which their phases are adjusted so that relative displacement amounts between the read heads are eliminated are previously recorded onto the data surfaces of the plural media each head and cylinder position.
The phases of the phase servo patterns are adjusted so that relative displacement amounts of another read heads with respect to a specified read head are eliminated, and the phase servo patterns are recorded on the data surfaces of the plural media. More concretely, the previously measured relative displacement amounts D of another read heads with respect to a specified read head are converted into phase angles xcfx86 of the phase servo patterns in each cylinder position of each head, the phase servo patterns are previously recorded onto the media surfaces of the specified read head in each cylinder position in a state that the phase angle xcfx86 is zero, and the phases are displaced by the phase angles xcfx86 so that the phase servo patterns are previously recorded onto the media surfaces of the read heads other than the specified read head.
In addition, in another form of respective data surfaces of the plural media provided in the storage device, the phases of the phase servo patterns are adjusted so that relative displacement amounts (measured displacement amount) D of the read heads with respect to the write heads are eliminated, and the phase servo patterns are previously recorded. More concretely, the phase servo patterns are displaced by the phase angles xcfx86 of the phase servo patterns converted from the previously measured displacement amounts D in each cylinder position of each head so that the phase servo patterns are previously recorded.
In the case where the phase servo patterns are recorded onto the data surfaces of the plural media provided in the storage device in a state that N cylinders form 1 unit, the phase angle xcfx86 is calculated from the displacement amount (xcex1 or D) according to the following equation:
xcfx86=(360xc2x0/N)xc2x7(displacement amount).
Cylinder information to be written with the phase servo patterns is offset from a track center according to the displacement amounts of the read heads with respect to the write heads in each head and each cylinder position so as to be previously recorded further onto the data surfaces of the plural media provided in the storage device. In the case where the phase servo patterns are displaced by (1/n) track pitch unit for 1 cylinder in a state that N cylinders form 1 unit so as to be recorded, the displacement amounts of the read track center are converted into head feeding amounts of the (1/n) trackpitch unit, and the cylinder information which is subject to offset seek is previously recorded onto the data surfaces of the plural media provided in the storage device. In the case where the cylinder information which is recorded without offset seek is adjacent to the cylinder information which is offset-recorded, one of the cylinder information is narrower than 1 track width and the other one is wider than 1 track width.
(Track Seek by Phase Adjustment at the time of Switching Heads)
Another embodiment of the present invention provides a servo information writing method which utilizes a function for correcting position signals by means of phase adjustment of phase servo patterns, and facilitates a seek operation for sequential access or the like for switching heads successively between continuous plural cylinders so as to improve an access performance. Namely, the servo information writing method of discretely recording servo information including phase servo patterns in a track direction onto data surfaces of plural media in a storage device in which heads integrally having write heads and read heads corresponding to the data surfaces of the plural media, is characterized in that in the case where a number of heads corresponding to the media surfaces is M, the phases of phase servo patterns are displaced by (1/M) track pitch in an order of the head numbers in the same cylinder positions of the media surfaces and the phase servo patterns are written so that position information read from the phase servo patterns by the read heads is displaced by the (1/M) track pitch in the order of the head numbers. For this reason, in the case where the final head in the No. i cylinder is switched into a front head in the next No. (i+1) cylinder, conventional 1-track seek which requires a high-order command is not utilized, offset seek of 1/M track pitch which requires only an internal process of the storage device may be utilized. As a result, an access performance can be improved.
Here, in the case where the phase servo patterns are recorded in the state that N cylinders form 1 unit, a phase angle xcfx86 corresponding to the (1/M) track pitch is calculated according to the following equation:
xcfx86=(360xc2x0/N)xc2x7(1/M)
and the phase servo patters are displaced by the phase angle xcfx86 in the order of the head numbers so as to be written in the same cylinder positions of the media surfaces. For example, in the case where a number of the heads is four and the phase servo patterns are recorded in unit of four cylinders, the phase servo patterns are displaced by the phase angle xcfx86 of 22.5xc2x0 in the order of the head numbers so as to be written. As for the adjustment of the writing phases of the phase servo patterns, the phase angle xcfx86 is converted into delay time xcfx84d so as to be set in the programmable delay line, and phases of writing reference clocks read from the media surfaces are changed.
Further, the present invention provides an apparatus in which a plurality of heads integrally having write heads and read heads corresponding to data surface of plural media are located in arbitrary cylinder positions and performs recording/reproduction, and servo information including phase servo patterns is recorded discretely in a track direction onto the data surfaces of the plural media, characterized in that in the case where a number of heads corresponding to the media surfaces is M, phases of the phase servo patterns are displaced by (1/M) track pitch in an order of the head numbers in the same cylinder positions of the media surfaces and the phase servo patterns are previously recorded onto the data surfaces of the plural media so that position information read from the phase servo patterns by the read heads is displaced by (1/M) track pitch in the order of the head numbers. Also in this case, in the case where the phase servo patterns are recorded in a state that N cylinders form 1 unit, the phase angle xcfx86 corresponding to the (1/M) track pitch is calculated according to the following equation:
xcfx86=(360xc2x0/N)xc2x7(1/M),
and the phase servo patterns are displaced by the phase angle xcfx86 in the order of the head numbers in the same cylinder positions of the media surfaces so as to previously recorded onto the data surfaces of the plural media.